One problem facing cardiac surgeons is lack of suitable devices to provide temporary cardiac support to neonates and pediatric aged patients. Existing devices used clinically (ECMO and centrifugal pumps) are too large relative to the size of the patient. The specific aims of this program focus on demonstration of a new rotary pump intended solely for these special young patients. Nimbus' latest creation is a very small, inexpensive centrifugal blood pump for adult cardiopulmonary bypass procedures. Extensive in vitro testing verifies that this pump is equivalent in flow performance and hemolysis generation to existing centrifugal devices. Preliminary studies which form the basis of this Phase I proposal show that the Nimbus pump adapts readily to a neonatal/pediatric version. The key innovation is that the resulting pump size (15 cc priming volume) is 1/5 to 1/3 that of existing centrifugal pumps. This Phase I study will evaluate this pump concept through in vitro testing of flow performance, hemolysis generation, and shaft seal integrity. In vivo tests, to be performed at the University of Pittsburgh, are intended to demonstrate the hemodynamic performance, biocompatibility and general suitability of this pump for neonatal/pediatric applications. A Phase II study would involve longer in vivo trials and development of the pump and its control as a clinical product.